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LogicDictates
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Travel times in the expanseThe Expanse novels

I am wondering about the travel times in the Expanse novelsThe Expanse novels, and not for the first time.

I am currently at the beginning of book 4, Cibola Burn (2014), and the Rocinante has passed the ring, traveling to Illus/New Terra. Alex announces that they can arrive after a flying time of over 70 days on a high burn.

But here is the problem: The math does not seem to make any sense. Suppose they fly at a constant acceleration A for the first half of the trip, turn the ship around and fly at a constant deceleration -A for the second half of the trip (this is the standard travel mode in the ExpanseThe Expanse, as is repeatedly said). Then after time t, they would have traveled the distance x(t) = 2A(t/2)^2. Suppose that A=g, the acceleration due to gravity on earth (which would certainly not be a "high burn" schedule), then they would travel 1199 AU in 70 days. (Just plug *"2 * (35 days)^2 * acceleration due to gravity in astronomical units" into Wolfram Alpha). On high burn, they would get much faster. It is not said how far out the ring is in the solar system of Illus, but 1199 AU is very far out.

The 18 month travel time for the research vessel to reach Illus from Luna are also not realistic. In this time, they would have traveled many thousand AU.

In novel 3, Abaddon's Gate (2013), it is mentioned that the Rocinante needs around 3 months travel time to reach the ring from Ceres. At 1g, the Rocinante would travetravel 1982 AU in this time, and still 660.6 AU at 1/3*g. But the ring is between the orbit of Neptune and Uranus, so certainly less than 30 AU out. So these numbers do not match up, even if the ring was at the opposite side of the sun from Ceres at the beginning of the journey. 660 AU is far outside the sun's heliosphere.

Also in novel 3, it is said that it would take "only" 12 days to reach Mars from earthEarth if the orbits are aligned, when really, it would take not even 2 days at 1g.

I am very confused by this, because I was under the impression that the scientific facts of the books are very well researched. I cannot understand why this rather simple math would be so far off. Am I missing something?

Travel times in the expanse

I am wondering about the travel times in the Expanse novels, and not for the first time.

I am currently at the beginning of book 4, and the Rocinante has passed the ring, traveling to Illus/New Terra. Alex announces that they can arrive after a flying time of over 70 days on a high burn.

But here is the problem: The math does not seem to make any sense. Suppose they fly at a constant acceleration A for the first half of the trip, turn the ship around and fly at a constant deceleration -A for the second half of the trip (this is the standard travel mode in the Expanse, as is repeatedly said). Then after time t, they would have traveled the distance x(t) = 2A(t/2)^2. Suppose that A=g, the acceleration due to gravity on earth (which would certainly not be a "high burn" schedule), then they would travel 1199 AU in 70 days. (Just plug *"2 * (35 days)^2 * acceleration due to gravity in astronomical units" into Wolfram Alpha). On high burn, they would get much faster. It is not said how far out the ring is in the solar system of Illus, but 1199 AU is very far out.

The 18 month travel time for the research vessel to reach Illus from Luna are also not realistic. In this time, they would have traveled many thousand AU.

In novel 3, it is mentioned that the Rocinante needs around 3 months travel time to reach the ring from Ceres. At 1g, the Rocinante would trave 1982 AU in this time, and still 660.6 AU at 1/3*g. But the ring is between the orbit of Neptune and Uranus, so certainly less than 30 AU out. So these numbers do not match up, even if the ring was at the opposite side of the sun from Ceres at the beginning of the journey. 660 AU is far outside the sun's heliosphere.

Also in novel 3, it is said that it would take "only" 12 days to reach Mars from earth if the orbits are aligned, when really, it would take not even 2 days at 1g.

I am very confused by this, because I was under the impression that the scientific facts of the books are very well researched. I cannot understand why this rather simple math would be so far off. Am I missing something?

Travel times in The Expanse novels

I am wondering about the travel times in The Expanse novels, and not for the first time.

I am currently at the beginning of book 4, Cibola Burn (2014), and the Rocinante has passed the ring, traveling to Illus/New Terra. Alex announces that they can arrive after a flying time of over 70 days on a high burn.

But here is the problem: The math does not seem to make any sense. Suppose they fly at a constant acceleration A for the first half of the trip, turn the ship around and fly at a constant deceleration -A for the second half of the trip (this is the standard travel mode in The Expanse, as is repeatedly said). Then after time t, they would have traveled the distance x(t) = 2A(t/2)^2. Suppose that A=g, the acceleration due to gravity on earth (which would certainly not be a "high burn" schedule), then they would travel 1199 AU in 70 days. (Just plug *"2 * (35 days)^2 * acceleration due to gravity in astronomical units" into Wolfram Alpha). On high burn, they would get much faster. It is not said how far out the ring is in the solar system of Illus, but 1199 AU is very far out.

The 18 month travel time for the research vessel to reach Illus from Luna are also not realistic. In this time, they would have traveled many thousand AU.

In novel 3, Abaddon's Gate (2013), it is mentioned that the Rocinante needs around 3 months travel time to reach the ring from Ceres. At 1g, the Rocinante would travel 1982 AU in this time, and still 660.6 AU at 1/3*g. But the ring is between the orbit of Neptune and Uranus, so certainly less than 30 AU out. So these numbers do not match up, even if the ring was at the opposite side of the sun from Ceres at the beginning of the journey. 660 AU is far outside the sun's heliosphere.

Also in novel 3, it is said that it would take "only" 12 days to reach Mars from Earth if the orbits are aligned, when really, it would take not even 2 days at 1g.

I am very confused by this, because I was under the impression that the scientific facts of the books are very well researched. I cannot understand why this rather simple math would be so far off. Am I missing something?

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Matthias Ludewig
Matthias Ludewig
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Travel times in the expanse

I am wondering about the travel times in the Expanse novels, and not for the first time.

I am currently at the beginning of book 4, and the Rocinante has passed the ring, traveling to Illus/New Terra. Alex announces that they can arrive after a flying time of over 70 days on a high burn.

But here is the problem: The math does not seem to make any sense. Suppose they fly at a constant acceleration A for the first half of the trip, turn the ship around and fly at a constant deceleration -A for the second half of the trip (this is the standard travel mode in the Expanse, as is repeatedly said). Then after time t, they would have traveled the distance x(t) = 2A(t/2)^2. Suppose that A=g, the acceleration due to gravity on earth (which would certainly not be a "high burn" schedule), then they would travel 1199 AU in 70 days. (Just plug *"2 * (35 days)^2 * acceleration due to gravity in astronomical units" into Wolfram Alpha). On high burn, they would get much faster. It is not said how far out the ring is in the solar system of Illus, but 1199 AU is very far out.

The 18 month travel time for the research vessel to reach Illus from Luna are also not realistic. In this time, they would have traveled many thousand AU.

In novel 3, it is mentioned that the Rocinante needs around 3 months travel time to reach the ring from Ceres. At 1g, the Rocinante would trave 1982 AU in this time, and still 660.6 AU at 1/3*g. But the ring is between the orbit of Neptune and Uranus, so certainly less than 30 AU out. So these numbers do not match up, even if the ring was at the opposite side of the sun from Ceres at the beginning of the journey. 660 AU is far outside the sun's heliosphere.

Also in novel 3, it is said that it would take "only" 12 days to reach Mars from earth if the orbits are aligned, when really, it would take not even 2 days at 1g.

I am very confused by this, because I was under the impression that the scientific facts of the books are very well researched. I cannot understand why this rather simple math would be so far off. Am I missing something?